1, 25-Dihydroxyvitamin D3 activates Apelin/APJ system and inhibits the production of adhesion molecules and inflammatory mediators in LPS-activated RAW264.7 cells

Abstract Background 1, 25-Dihydroxyvitamin D3 (1, 25(OH) 2 D 3 ), an active form of vitamin D3, plays a crucial role in the mitigation of inflammation damage. Recent studies have revealed that apelin and its receptor (apelin/APJ system) could significantly ameliorate LPS-induced inflammation-response. This investigation aimed to appraise the effects of 1, 25(OH) 2 D 3 on the apelin/APJ system and production of adhesion molecules and inflammatory mediators in LPS–activated RAW264.7 macrophage cells. Methods Murine RAW264.7 cells were pretreated with 1, 25(OH) 2 D 3 , followed stimulation with LPS (1 µg/mL) for 24 h. The effect of 1, 25(OH)2D3 on LPS-induced cell injury was determined by MTT assay, whereas, enzyme-linked immunosorbent assay (ELISA), qPCR and western blotting were used to evaluate cytokine production and apelin/APJ system expression. Intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) protein expression were measured by flow cytometry. Results The levels of IL-1β, IL-6, and TNF-α cytokines were significantly increased by incubation with LPS. LPS also increased the protein expression of adhesion molecules, including VCAM-1 and ICAM-1. However, pretreatment with 1, 25(OH) 2 D 3 markedly inhibited LPS-induced production of inflammatory cytokines and adhesion molecules. Moreover, we found that 1, 25(OH) 2 D 3 could induced the apelin/APJ system expression. Further experiments demonstrated the significant increase of apelin/APJ system expression at both the protein and mRNA levels in LPS-activated cells when pretreated with 1, 25(OH) 2 D 3 . Conclusion Taken together, our results indicated that 1, 25(OH)2D3 confers an anti-inflammatory effect through a likely mechanism involving a reduction in pro-inflammatory mediators and adhesion molecules via up-regulation of the apelin/APJ system in RAW264.7 cells.